Decay of Water Waves Due to Floating Balls with Application to Simulating Wave Decay in the Marginal Ice Zone

An experimental study is conducted to investigate the decay of free-surface water waves in a sloshing tank with partially-submerged floating plastic balls on the free surface. The present study is motivated by the need to understand possible mechanisms for ocean wave decay in the marginal ice zone. The existing theoretical and numerical studies lack in modelling the complex dynamics of ocean wave-ice interaction in the marginal ice zone. Hence, in the present study, laboratory experiments are performed to explore the underlying prominent physical processes and estimate the wave decay rate due to floating balls representing ice-floes. The decay rates of the free surface wave amplitudes are obtained for two cases: free surface with and without floating balls, and it is shown that the floating balls significantly enhance the decay rates. The temporal decay rates of the free surface wave amplitudes are measured for a small amplitude of excitation and different water depths. The decay rates for the first and third sloshing modes are extracted, even when they are combined. It is shown that the decay rates obtained from the present study match with the exponent three power-law dependence on wave frequency as observed for the decay rates in the marginal ice zone. This matching of exponent suggests that the same mechanism is responsible for both types of decay.